What should you know about black steel pipes?

Black steel pipes are a common material for transporting natural gas and water. They are used in both domestic and commercial applications and are generally stronger than other materials such as PVC. The composition and properties of black steel pipes make them well-suited for certain applications, but not entirely suitable for all. If you plan to use black steel pipes, it's best to understand the following information about them.

Basic properties of black steel pipes

Material: Carbon steel

Surface Condition: Black skin (iron oxide layer), ungalvanized

Common Standards: ASTM A53 Gr.B / ASTM A106 Gr.B / EN 10255

Connection Methods: Threaded connection, welding (some industrial applications)

Main Uses: Natural gas, steam, fire protection, structural support

Why is it called black steel?

The "black" color of black steel pipes is not formed by painting or spraying, but comes from the manufacturing process.

During hot rolling or hot forming, a layer of iron oxide (mill scale) naturally forms on the surface of the steel pipe. Its main components include FeO, Fe₃O₄, and Fe₂O₃. This oxide layer has a deep black or bluish-black appearance, hence the name "Black Steel Pipe."

When to use black steel pipe?

Natural gas and liquefied petroleum gas (LPG) transmission systems;

Steam and heating pipelines;

Fire sprinkler systems;

Industrial plant and equipment structural support;

Indoor mechanical and process piping.

How to install black steel pipe?

1. Cutting and Tapping

Secure the pipe in pipe wrenches on a bracket and cut it using a pipe cutter with a rotary cutting blade. It is recommended to use high-quality cutting oil to protect your pipe cutter.

2. Connecting Fittings

Black steel pipe is connected using fittings and connectors. In typical gas pipeline installations, Teflon tape or pipe sealant should always be applied to the threads to ensure no leaks occur.

First, tighten the pipe by hand, then use two pipe wrenches (one for the pipe and one for the connector) to tighten the joint. If the pipe is found to be too loose, it may need to be recut. Learn more.

Is there a difference between black steel pipes and galvanized pipes?

The main difference between black steel pipes and galvanized pipes is that they are both made of steel, which can be confusing for some. Galvanized pipes have a layer of zinc compound coated on the surface of the steel pipe, which helps improve its corrosion resistance and durability. This coating is also the reason why galvanized pipes are more expensive.

Black steel pipes do not have this coating, nor even paint. Their black color comes from iron oxide produced during the manufacturing process. Black steel pipes are widely used for gas and water transportation, but with the application of other materials such as PVC in the water pipe sector, black steel pipes are more often used for gas transportation.

Will black steel pipe rust?

Another reason why black steel pipes are more suitable for gas transportation is that they lack a rust-proof protective coating. Due to frequent contact with water, even in humid environments, black steel pipes are prone to rusting.

How to prevent black steel pipes from rusting? You can apply a protective black pipe coating, but the simplest protection method is painting, or wrapping them with anti-corrosion tape.

Is black steel pipe okay for water?

While black steel pipes are sometimes used to transport water, they should never be used to transport drinking water, as metal corrosion will cause rust to seep into the drinking water. They are best suited for closed-loop hydraulic heating and steam heating systems because they are not constantly exposed to oxygen. They are also commonly used as electrical conduits.

How long does black steel pipe last?

The lifespan of black steel pipes is not a fixed number; it depends primarily on the environment in which they are used, anti-corrosion measures, and maintenance.

Indoor gas pipelines (dry environment): Approximately 30–50 years

Closed heating/steam systems: Approximately 20–40 years

Industrial plant structural uses: Approximately 25–50 years

Outdoor exposure, without anti-corrosion: Approximately 5–10 years

Underground installation (without anti-corrosion): Approximately 2–5 years

Underground installation (with anti-corrosion coating): Approximately 10–15 years or more

Does black steel pipe require additional protection when laid underground?

Since one of the primary uses of black steel pipes is to transport natural gas, burying them underground should be considered. This is especially important if you are supplying gas or water to rural areas.

While these pipes are inherently heat-resistant, underground environments are often damp or susceptible to moisture. Burying black steel pipes underground is not recommended unless the surface is coated with a protective layer to prevent oxidation.

With moisture protection, the metal's durability plays a significant role, allowing it to last over 10 years underground. Without protection, it won't last that long.

What pressures and temperatures can black steel pipes withstand?

Like all pipes, black steel pipes have their pressure limits. They typically transport natural gas or propane, both of which are usually below 60 psi. This is well below the 150 psi pressure standard that must be adhered to for proper installation of black steel pipes. If you use high-quality black steel pipes, they should be able to withstand these pressures.

As mentioned earlier, black steel pipes are inherently heat-resistant. Its melting point is typically above 538°C (1000°F), but commonly used joint sealing tapes fail at around 260°C (500°F). Even if the pipe can withstand higher temperatures, leaks will begin if the sealing tape fails.

The good news is that normal weather or natural conditions don't reach such high temperatures. Therefore, unless your pipe is near machinery that generates extremely high temperatures, you don't need to worry about it failing due to heat.

Is black steel pipe easy to install?

Black steel pipe is easy to install because it has seams and can be connected using only a series of fittings, without welding. Since black steel pipe is cheaper than galvanized pipe and requires no welding, it is an economical option.

Black steel pipe has good ductility, meaning it can be easily threaded and connected to other components without any problems. Black steel pipe is a good material, but should be avoided in environments prone to corrosion or rust.

Summary

In summary, black steel pipe remains the mainstream choice for global gas and industrial piping systems due to its high strength, high temperature resistance, ease of installation, and cost advantages. Only by correctly understanding its performance limits and using it in the appropriate environment can its engineering value and service life be maximized.

Read more: ERW VS. Seamless black steel pipe or Seamless black steel pipe schedule 40